Introduction: 15 Minutes SMS Door Entry Alarm

Picture of 15 Minutes SMS Door Entry Alarm

hi guys this is my first instructable i hope you'll enjoy it !!

Got sick of the high prices of Home Security systems ??
have old mobile sets don't know what to do with ?
build a cheap alarm system that will notify you on your mobile by SMS.
ready ??

grab the tools !

Step 1: What You'll Need

Picture of What You'll Need

An old mobile phone set with supply (charger).
Cheap door magnetic alarm (can be replaced by a magnetic switch and a magnet ).
5 volts Relay.
Soldering iron.
wires and thin insulated copper wires.
micro driller.
micro screwdriver set.
Scotch tape.

Step 2: Let's Get to Work

Picture of Let's Get to Work

here is the whole write the text message " for example : the main door was opened " then you put your mobile number then you...don't press the sending button.... you'll make the burglar do it !
you just want the magnetic switch to work as the sending button.

but unfortunately most of the alarms on the market contains an NO "normally-open" magnetic switch
so when the magnetic field applies "that means the door is closed ", the switch closes. and that means also that when the door is opened the magnetic field vanishes and the switch is opened..
we need the opposite of that we need the switch is closed when the door is opened and vise versa

what will we do ?? you can just seek a SPDT "Single Pole Double Throw" magnetic switch from components shops this should solve the problem of the whole alarm, but this was hard to find so i used a relay powered by the mobile charger to do the job..

The other problem is that some mobile sets closes the keypad automatically or switch to standby mode after a period of time "in order to save energy" but most of old ones doesn't... you just have to go to settings and turn of the automatic keypad lock.

if your mobile does closes the keypad automatically or switches to stand buy mode then you'll have to build a small 555 timer circuit that will trigger any unvital key on the keypad like the volume control " every 3 sec for example " to keep it on the send message mode.. of course the mobile should be powered from the charger all the time.

Step 3: Preparing the Mobile Set...

Picture of Preparing the Mobile Set...

Most of Nokia old mobiles are easy to deal with they don't standby and you can disable the auto keypad lock .
I used nokia 6210 and soldered two wires to the OK button "Upper left":

Step 4: Preparing the Magnetic Alarm...

Picture of Preparing the Magnetic Alarm...

In this step you'll just solder two wires to the two terminals of the magnetic switch inside.
and drill two holes for the two wires
the batteries in the alarm aren't necessary at all unless you want to keep the noisy alarm

NOTE : you have to test your alarm first, you may not need a relay at all test the magnetic switch with the multimeter to know whether it is NC or NO.

Step 5: Prepairing the Relay and Final Connection

Picture of Prepairing the Relay and Final Connection

The relay is simply a switch which is turned on or of by an electrical magnet when you apply current on the coil it operates the relay
but the problem is that the relay coil needs power to work , a good idea is to take the DC of the charger
"as the mobile will be always be connected to the charger "

Step 6: Test It Now ....

Picture of Test It Now ....

After checking the wiring and preparing the text your alarm system should be ready
just mount the the magnet on the door and the set on the frame , plug the charger into mains , switch on the mobile open the message and put the mobile number...

of course it's better to mount it in casing or something ...

now it's ready !

waiting for your comments and suggestions : )


datoo786 (author)2017-05-24

Hi there,

This is an interesting project.

I have two question to ask you.

Can a reed switch (NC) be soldered to the speed dial button without the need of a relay?. Here is a link:

What other phones are possible to soldered, apart from Nokia.


UDARA THILINAW (author)2016-04-13

Hi, good job, during a month of a period i was tried to find how to make this kind of a thing enabled with sms, thanks a lot for sharing these experiments with all of us. i want to make a employee suggestion box by using this tool, that's why i was search this type of tool. i think it possible to make a SMS alert system when some one drop their suggestions in to the box. if you have any other tools which can help to that, please send it to me., again thank you..

UDARA THILINAW (author)2016-04-13

Hi, good job, during a month of a period i was tried to find how to make this kind of a thing enabled with sms, thanks a lot for sharing these experiments with all of us. i want to make a employee suggestion box by using this tool, that's why i was search this type of tool. i think it possible to make a SMS alert system when some one drop their suggestions in to the box. if you have any other tools which can help to that, please send it to me., again thank you..

ehsan55 (author)2015-10-31

حرامي هههه

Youssefe10 (author)2015-09-30

good job ,
and from where in cairo i can buy this tools

graveyard_86 (author)2014-12-22

where did you buy the door magnetic alarm in Cairo ?

udaykumarravada (author)2014-04-12

you have done a nice but only nokia phones only suppourt thats only bad luck

vkushwaha1 (author)2014-03-23

intelligent.. but how sms will send??? it may be that sms will send due to continue press of ok button of Nokia phone... but is it working on other phones??

carlotuns00 (author)2014-03-15

can i know what is findings and specific objectives of this device my pleasure to know.

araps (author)2013-12-07

Men like you, make the world go round! keep going!

Mahmoud Alaa (author)2012-01-18

hey i am Egyptian too i am very glad that Egyptian people in instructables

Ayman_Alqdah (author)2011-05-29

مشكووووووووووووووووووور اخوي على هل المشروع الاكثر من رائع وانا بحيك من الاردن وان شاء الله للامام ونشوف اشي جديد

نعبدالرحمن (author)2011-05-24

MSA ya Mostafa keep on, and I'm sure that someday you will be a great inventor ;). Bas sa3tha mtt3allish 3alina :DD

miffy1297 (author)2009-11-08

Hi Am I missing something , Once the switch is made , does this not mean that the send button is effectively on all the time. I am thinking of using the system on my old boat , to warn of water ingress , but the switch would make once only , whereas you really want a pulse to operate the phone.
any ideas.

PanadoL (author)miffy12972009-11-10

No once the message is sent "in most mobiles " it wont be sent again
you have to "re-trigger" the switch to send the SMS again,
for your application you can also make a very simple digital circuit to send one pulse and stops working,on this way you wont need to "re-trigger" the system to make it work again.

miffy1297 (author)PanadoL2009-11-10

Many thanks will rig up a circuit and try this.

waddellm (author)miffy12972011-03-14

Hi Miffy,

I am wondering if you ever got this to work for your old boat. I arrived at the same instructable because I am trying to do the exact same thing to warn me if the bilge pump is running, or if the water level gets too high on my vintage boat.

Any help you can offer would be great!


miffy1297 (author)waddellm2011-03-15

Hi waddellm

Yes I have had this system working on my boat for the last two years. The only problem I had was keeping the phone battery charged . as I can leave the boat for several months over the winter, All I did was connect the bilge switch do the phone contacts , unfortunatly it was never tested as I have not had a leak.
Best wishes Andy

miffy1297 (author)2009-12-03

Has anyone managed to connect wires to the light or sounder on a phone in order to switch anything on via a phone, any ideas.

roland985 (author)miffy12972011-02-14

Oooh, Oooh, I know. A BOMB!!!

PanadoL (author)roland9852011-02-17 me... :o

PanadoL (author)miffy12972009-12-03

Yup...I've tried 2 ways, use a photo-resistor with circuit on the phone's display
and put them in a sealed box, when the phone receives a call its display will emit light, this light will operate the circuit. VERY SIMPLE
another way which I've tried but it's more complicated , is by using DTMF receiver circuit through phone's headset and controlling 10 relays through the caller's phone keypad.
for sharing any ideas or help with related projects, please contact me on my e-mail :

TheBestJohn (author)PanadoL2010-01-15

you could also arduino this to send an email to your cellphone... It would cost less than having a whole other phone's bill. As far as I know any cellphone provider gives their phone numbers email addresses.

I think a prepaid phone would be even cheaper.

miffy1297 (author)PanadoL2009-12-03

Thanks a lot , i had wondered whether this would work , I had tried connecting to the vibrator in the phone but this proved too tricky,

manutea (author)2011-02-15

Nice instructables, I love its simplicity!
thanX 4 sharing this project

timotb (author)2010-04-27

I love the High School Ingenuity. (Yes, that is a compliment.)  .  If you guys  can get together and build a simple refined device that will use the cellular system to send a SMS alarm message, like what we see here only with refinement.....let me know.....there is a market for a cheap alarm notifier..

jules15 (author)2010-04-20

PanadoL, where did you get those special tools to open the phone case?

hunterbait93 (author)2010-02-19

 instead of doing the weird stuff with the magnetic switch, just set it on the door frame and put a magnet into the door so it passes, duh

jules15 (author)hunterbait932010-04-20

i tried that last year and the relay is much easier

aussa (author)2010-04-05

Nicely done, I would recommend adding the wires to number button and adding your number to a speed dial assigned to that specific button. I made a similar thing in my car. But is triggered by the car alarm system ( in case I am away and cant hear the alarm)

hunterbait93 (author)2010-02-19

 maybe you could make an electromagnet with a concealed switch outside the door so you can turn it on and off

macobt (author)2009-09-05

Good,instead mesage you can make a call to number from speed dial number on the keyboard,same schematic just conect the wires to pin numbers from 1 to 9,and when a door is open one of speed dials are presed and call too desire number,even you can answer too this call and listen what is hapening. regards macobt

PanadoL (author)macobt2009-09-05

yea it's cooler idea... it won't even use credit or cost you anything. even if the door was closed and opened again this will release the key and trigger it again so you'll receive another call and the system won't need setting up again every time you come in and out this will also solve the problem of how you'll get out of the house without an SMS being sent every time... Thanks for your valuable suggestion Macobt I'll probably update the instructable and refer to your comments. Regards

versanil (author)PanadoL2009-09-11

You could connect a loudpeaker and talk to the robber. Suggest alternative sources of income XD

PanadoL (author)versanil2009-09-11

LOL ,You know what , that may frighten him and he'll run away then :D :D really nice idea :D

macobt (author)PanadoL2009-09-11


jiyoonasan (author)macobt2010-02-06

 sir please help me with my thesis.. i am willing to learn that thing its because it will be useful for our thesis authomated door access i hope u can help us.. sir, it case i am requesting for some video or screen shots on how to do that.. tnx a lot.. hoping for your reply..tnx.

macobt (author)jiyoonasan2010-02-06

first tell me whether you have knowledge of electronics???

PanadoL (author)macobt2009-09-11

wow... that's much neater than mine :) what's that IC ??

macobt (author)PanadoL2009-09-11

Here is link to schematic very simple>
Regards Panadol

fkuk (author)PanadoL2009-09-05

just add a switch in the line and add that switch out side the door and one switch inside the room in a hidden location

Perhaps a hidden magnetic relay thingy; just hold a magnet to a spot on the door with a magnetic switch hidden on other side. But thats pushing it, probably better to just keep things simple.

sometimes simple things are better,but when you build a alarm for your house then we need something more intelligent,like this cell call when someone want to get in the house and you are alerted by call of your alarm and when you answer to call you may listen what is hapening.regards to all.

batman96 (author)macobt2009-09-08

All you have to do is call the phone as soon as you receive the "robber" txt msg. put the ringer on silent, and turn on auto answer. So you can listen in if you want to.

macobt (author)batman962009-09-11

why to do that,when the alarm is turn in on when is conected one of speed numbers and auto conecting to disere number,and you can answer the call and listen,another suggestion is to conect speaker phone to alarm to be louder when you speak,too scare the intruder.

TechXhacker (author)2010-01-24

You do not need the alarm to send the message. Simply remove the small green, which is the magnetic sensor, and paste on the side of the phone. The magnet will be laid at the door, and when someone opens the OK button is pressed. Only has the disadvantage that when placed in the door can only be disabled after entering the house, which creates a cost (it's expensive!). A tip: put a switch activated by key on the outside wall, using an existing passage (a conduit, for example).
Or, you can think big, and put a remote control, connected to a relay! (Not so expensive, and it is sold ready for use). But the idea was good. I had thought about it but thought it would not work.

sulphurissweet (author)2009-10-20

can u help me with where to connect the wires. that is which wire to which terminal of the relay

ibuildcrap (author)2009-09-11

This is cool but it will only work ONCE after the door is opened which will make it send the message. A much more reliable method would be to connect an arduino to the magnetic switch and make a simple program to send the computer a number if the switch is opened over the usb cable. On the computer side you could pick from a bunch of different languages like, arduino ect... But what you would do is write a program on the computer that listens on the usb (serial port) and if it reads the specific number from the arduino like 2 for door open then it would send an email BUT when you send the email it would be yourphonenumber@yourcarriersemail2text for example <-- this will send a text message to that number if it is a VERIZON wireless phone most carriers have this email to text service, just look up your exact carriers.

PanadoL (author)ibuildcrap2009-09-11

Nice.. I was having many options but I was just looking for THE SIMPLICITY and something that any one can build easily with out knowing almost any thing about electronics or programming, I worked with Parallel port before and I made a remote control via the telephone line fax modem to send DTMF to a mobile phone during the call, the DTMF is received from the headphones to a DTMF decoder then to a BCD to decimal decoder then to the 10 relays set using visual basic was very easy and reliable for this application , If anyone need help with building a project like this or upgrading this project just contact me... Regards to all

About This Instructable



Bio: My name is Mostafa I live in Cairo, Egypt and I'm Egyptian, I'm an Engineering Student, Department of Energy and renewable Energy at ... More »
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